What is the diagnosis and management for an elderly man with a worsening lesion on his left forehead over 12 months, containing a worm, and potentially related to underlying skin cancer or other comorbidities, such as diabetes or immunocompromised states?

Cutaneous Sparganosis with Secondary Infection

This is cutaneous sparganosis—a parasitic infection caused by the plerocercoid larva of Spirometra tapeworm—and requires immediate surgical excision of the worm and surrounding tissue, which is the only curative treatment. 1, 2

Diagnosis

The clinical presentation is pathognomonic for sparganosis:

• A slowly progressive subcutaneous mass over 12 months that becomes ulcerated and contains a visible worm is characteristic of cutaneous sparganosis 1
• The forehead is a recognized location for this infection, though less common than other body sites 1
• Patients typically acquire infection through consumption of contaminated water containing infected copepods, eating raw or undercooked frogs/snakes, or applying frog/snake poultices to wounds 3, 4
• The "worm" visible in the wound is the plerocercoid larva (sparganum) of Spirometra species 1, 2

Key diagnostic pitfall: This can initially mimic skin cancer, cyst, or abscess, leading to delayed diagnosis and inappropriate antibiotic treatment 1. The presence of a visible worm and the migratory nature of the lesion (if it changes location) are distinguishing features.

Immediate Management

Surgical excision is the definitive and only reliably curative treatment:

• Complete surgical removal of the live worm along with surrounding granulomatous tissue is essential for cure 2
• Incomplete removal leads to progression of symptoms and treatment failure 2
• The worm may be motile during surgery 4
• Send the specimen for both morphological identification and molecular analysis (mitochondrial COX1 and 28S rRNA genes) to confirm Spirometra species 4

Medical therapy with praziquantel is NOT effective:

• Multiple studies demonstrate that praziquantel has no killing effect on live Spirometra worms 2
• Patients treated with praziquantel alone showed progression of disease and uncontrolled symptoms 2
• Do not delay surgery to attempt medical treatment 2

Wound Management

• Treat secondary bacterial superinfection with appropriate antibiotics based on wound culture 5
• Provide local wound care until surgical excision can be performed 5
• The elderly patient's comorbidities (likely diabetes given the clinical context) may complicate wound healing and increase infection risk 5

Evaluation for CNS Involvement

Critical consideration: While this appears to be isolated cutaneous disease, cerebral sparganosis can occur and presents with seizures, headaches, and focal neurological deficits 3, 6, 2

• Obtain a careful neurological history and examination 3, 2
• If any neurological symptoms are present (seizures, headaches, focal deficits), obtain brain MRI, which is the most valuable modality for detecting cerebral sparganosis 2
• Characteristic MRI findings include widespread white matter degeneration, mixed-signal lesions, and irregular enhancement that may change location on follow-up studies 2

Post-Surgical Follow-Up

• Patients who undergo complete surgical removal have favorable outcomes with resolution of symptoms 2
• Monitor the surgical site for complete healing 2
• Follow-up examination at 3-6 months to ensure no recurrence 2
• No additional antiparasitic medication is needed after complete surgical excision 2

Public Health Considerations

• Inquire about consumption of raw or undercooked frogs, snakes, or contaminated water 3, 4
• Educate the patient to avoid these exposures to prevent reinfection 4
• This is not transmissible person-to-person, so isolation is not required 3